(Reuters) - Democrat Barack Obama expanded his lead over Hillary Clinton in New Hampshire to 13 points as voting began in the state's critical presidential primary, according to a Reuters/C-SPAN/ Zogby poll released on Tuesday.
Republican Sen. John McCain of Arizona also widened his advantage over former Massachusetts Gov. Mitt Romney, taking a 36 percent to 27 percent edge after months of hard campaigning in the state.
Obama continued to feed on the momentum from his performance in Iowa last week, when he and Republican Mike Huckabee scored breakthrough wins that left Clinton and Romney reeling.
Obama , a senator from Illinois bidding to make history as the first black U.S. president, led the one-time Democratic front-runner 42 percent to 29 percent. Former North Carolina Sen. John Edwards was third with 17 percent.
" Obama is still on a roll and not slowing down. He had another big day," pollster John Zogby said.
Obama led Clinton in all categories of voters except women and voters over the age of 65, and was pulling away from the New York senator among base Democratic voters.
"This is the same thing he did in the closing hours in Iowa," Zogby said of Obama .
The rolling poll of 862 likely Democratic voters and 859 likely Republican voters was taken Saturday through Monday. It has a margin of error of 3.4 percentage points.
New Hampshire's primary on Tuesday is the next battleground in the state-by-state process of choosing Republican and Democratic candidates for November's election to replace President George W. Bush.
The pressure is on Clinton and Romney to revive their campaigns after disappointing showings in Iowa, and a second consecutive loss for either could doom their comebacks.
Clinton, a former first lady, finished third in Iowa. Romney, who at one time led polls in Iowa and New Hampshire, finished second.
While McCain gained more ground on Romney in the new poll, Huckabee has not been able to take advantage of his Iowa win. Huckabee , a Baptist minister and former Arkansas governor, held third at 10 percent.
Former New York Mayor Rudy Giuliani was tied for fourth in New Hampshire with Texas Rep. Ron Paul, an anti-war libertarian, at 9 percent. Former Tennessee Sen. Fred Thompson was at 2 percent.
"The question is whether Romney can pick up any more steam, because he did slightly better on the last day," Zogby said. "McCain still has strong leads among independents and among older voters."
The final day of polling came after Sunday's debate with his rivals, when Romney went on the offensive against Huckabee and McCain on taxes and immigration and was not the target he was in a debate on Saturday.
About 5 percent in each party remain undecided, according to the New Hampshire poll.
In the Democratic race, former New Mexico Gov. Bill Richardson was in fourth place at 5 percent, ahead of Ohio Rep. Dennis Kucinich at 2 percent.
The rolling tracking poll concludes with New Hampshire's voting on Tuesday. In a rolling poll, the most recent day's results are added while the oldest day's results are dropped in order to track changing momentum.